So far I don't believe I've heard anyone make the obvious case against method overloading -- that unless done very carefully indeed, it makes the code much, much more difficult to read. One method does one job is the sane way to go, thanks.
Or, indeed, the practical case - at the very heart of Ruby is the idea of duck typing. Duck typing rules out method overloading, because parameters would have to have set types before you could have a signature. Presumably no-one is suggesting that we should have fixed typing in Ruby?